The Spain centre-back has called for unity within the Real Madrid camp and admitted that his captain has suffered due to his time on the bench
The club captain sustained a hand injury in the Copa del Rey against Valencia in January, prompting the signing of Diego Lopez from Sevilla.
The former Villarreal man has since kept his place in the first team and Ramos says the Spain skipper has suffered due to his bit-part role.
"Casillas has had a tough time," the 27-year-old told reporters at the Mutua Madrid Open tennis tournament.
"We look back at a long friendship and relationship. Companions are good for both Casillas and the coach, as we all strive for the same goals. It's important that we are united."
Jose Mourinho claimed recently that his biggest regret of his time at Real Madrid was not replacing Casillas sooner, prompting defender Pepe to urge his boss to show more respect for the Spain skipper.